DODGE RAM FENDER PROBLEM

1996 Dodge Ram • 17,000 miles

Hi I have a 1996 dodge 2500 4wd truck and live in central Pa. On friday 12/28/2012 it snowed and I plowed with it in 4wd. When I parked it I placed back in 2wd. The next day it snowed and when I went out to plow again and putting it in 4wd it would not ingauge so I taped the actuator by the right wheel and it started to make a grrrrrrr sound and finly locked in. But all day it would pop in and out of 4wd. Is the trouble the actuator and if so how much of it needs replaced I see there are several parts thanks for any help